ro347

My Feedback: (13)

Hey guys. Ive been having issues with a saito 100 Ive had since new. After resolving some air leak issues with the carb by replacing gaskets and rubber seals, I came upon loss of all compression at the field after trying to reset the needles. With that I've discovered that the intake valve might be sticking a little, and is not seating tightly. The exhaust valve has a tight seal.

Im having a really hard time unscrewing the pins that hold the rocker arms in place. They wont budge. Can someone offer any help and tell me how to loosen these screws holding the rocker arms in place?

mscic-RCU

My Feedback: (6)

you might try just soaking the cylinder/head in glow fuel and see if you can free the sticking valve. I have also sprayed the valve and rocker arms with wd 40 and freed them up that way too. If the valve is just stuck, you don't necessarily have to remove it to free it.

Gray Beard

My Feedback: (-1)

Heat is your friend. There are a number of ways to get things hot, heat gun, small torch, or even boiling the parts in vegetable oil or the oven. A torch can also warp parts so if you try one be extra careful. Soaking in liquid wrench may also work but heat usually does the trick.
When I rebuild an engine I use a pan of boiling water and boil the engine completely so it all expands at the same time before I disassemble.

ro347

My Feedback: (13)

I tried a little heat, but I guess it just wasn't enough and needed a bit more. Either way, I realized that I could pull the valves and springs without removing the rocker arms. Hopefully this is the reason for loss of compression.

Ill keep the soaking in solution and boiling water tips in my pocket for next time.

Thanks guys!

Gray Beard

My Feedback: (-1)

A couple years back I had put away my favorite YS 110 wet for a long spell and when I pulled it out to use I had zero compression? The rockers and push rod were working but the valve itself was stuck opened? I had to open the engine then remove the valve so I could clean out all the crud then clean the valve stem. After that it fired right up. For a cheap thrill try getting those little keepers back on the valve!!! I finally made a little tool from piano wire, sort of a bent and filed tweezers that did the trick.
Heat would allow the valve to work but not for long, it had to be removed and cleaned.

ro347

My Feedback: (13)

Interestingly enough I was able to replace the clips despite my sausage fingers. It wasn't an issue. After reassembling I came to learn that it doesnt seem like the valve is actually sticking (I sat that because everything is clean as a whistle and oiled). Im still getting a faint notchy feeling when pressing down on the intake valve just as soon as it opens(one tick, right at opening only). But completely smooth on the exhaust side. Ive checked everything and all looks good. Valves are straight, cylinder is ok and whatever else. Im just not understanding what the problem could be.

So despite the slight notch feeling when pressing on the valve - I'm figuring that I might be splitting hairs here. I still need to figure out why I suddenly don't have compression. Im very meticulous about my stuff. So needless to say, once something goes wrong I go into some insane OCD mode. I NEED HELP! Gotta get this figured out.

Gray Beard

My Feedback: (-1)

Ring or valve is usually the problem with compression. Sometimes they lack compression but once started they run fine and the compression returns? I have been given several answers to this but none of them makes sense to me. Look at the push rods and make sure they are straight and the cam and crank to be sure there are no broken teeth. Maybe a sticking tappet?
Mine was obvious because the valve was stuck open and the engine wouldn't fire. If yours is running it may be nothing but that normal lack of compression that just happens.